January 25, 2024
January 25, 2024

MRI vs CT Scan: What’s the Difference?

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MRI vs CT Scan: What’s the Difference?

When it comes to health screenings, the differences between an MRI vs CT scan might not be clear. While CT scans and MRIs each create detailed images of the body, the key difference is that CT uses X-rays while MRI uses powerful magnets and radio waves.

Here, we’ll explore the distinctions between MRI (magnetic resonance imaging) and CT (computed tomography) scans, highlighting their applications, benefits, and considerations. We’ll also provide insight into how these imaging techniques provide valuable information for different medical conditions as well as for full-body health screening.

MRI vs CT Scan and Other Imaging Types

Medical imaging techniques visualize the body’s internal structures without invasive procedures to help in the diagnosis of various diseases. Among the most common medical imaging techniques include X-ray, positron emission tomography (PET), computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound.

Here’s a brief look at these techniques and how they are commonly used:

  • X-ray: This form of electromagnetic radiation can detect bone fractures, pneumonia, and dental problems
  • PET: PET scans are largely used in cancer staging but they can also be used to verify cellular activity in neurodegenerative and cardiovascular diseases 
  • CT: These types of scans can detect internal injuries, blood clots, and tumors
  • MRI: These scans can detect and evaluate soft tissue injuries, tumors, and diseases like multiple sclerosis
  • Ultrasound: This type of imaging is used for detecting and monitoring pregnancy, heart problems, and blood clots

MRI vs CT Scan: Benefits and Uses

While MRI and CT scans are both valuable medical imaging techniques, each has its distinct strengths and use cases. Here’s a closer look at the preferred uses of each imaging method.

When Is an MRI Useful?

There are a variety of situations when it’s useful to have an MRI. Here are just a couple of examples of what an MRI shows:

Soft tissues and organs: MRI has excellent contrast resolution, allowing for clear images of different types of tissues. This is beneficial for identifying abnormalities in most organs and soft tissues. MRIs provide detailed pictures of the brain, spinal cord, muscles, and joints, making them superior for evaluating neurological disorders, soft tissue injuries, and joint abnormalities.

Functional imaging: MRI is particularly valuable for functional imaging, including blood flow and brain activity studies. Functional MRI (fMRI) is widely used for neurological research and clinical applications.

One major advantage of MRI is that it does not use ionizing radiation. (More on this in a bit.) This makes it a safer option for imaging, especially when repeated scans are necessary over time.

When Is a CT Scan Useful?

Depending on the information the healthcare provider is trying to ascertain, a CT scan is useful. Here are a few examples:

Bones and calcifications: CT scans are highly effective in imaging bony structures. They provide excellent detail of the skeletal system, making them ideal for diagnosing bone fractures, tumors in bones, and other structural abnormalities.

Acute bleeding: CT scans are the go-to method for quickly assessing active internal bleeding, such as in cases of trauma or acute stroke. They can rapidly provide images to help evaluate the extent and location of bleeding.

Lung and chest imaging: CT scans more effectively image the lungs and chest area. They’re commonly used to diagnose and monitor lung diseases like pneumonia, emphysema, and cancer.

Cancer diagnosis and monitoring: Oncologists often prefer CT scans for diagnosing several types of cancer, including lung cancer, liver cancer, and pancreatic cancer. The scan provides detailed information about the size and location of the tumor, as well as whether the cancer has spread.

What to Expect When You Go for an MRI

MRI vs CT scan: MRI machine

MRI machines use powerful magnets and radio waves to create detailed images of the body's organs and tissues. MRI is particularly useful for imaging soft tissues like the brain, spinal cord, muscles, and ligaments. MRI does not use ionizing radiation, a key advantage over CT scans, especially for patients requiring multiple scans.

MRI scanners are large machines shaped like elongated donuts. They create a strong magnetic field and use radio frequencies that excite the water molecules in your body. The radio waves are sent to a receiver that produces an image revealing the possible presence of abnormalities in bones and soft tissues.

Patients with claustrophobia may have difficulty lying still in the machine for extended periods. If you have claustrophobia or get anxious in tight spaces, tell your technologist.

MRI scans can last from 15 minutes to an hour. If you’re bothered by loud noises, you can ask your radiologic technologist for earplugs or headphones — some facilities may offer the option to listen to your favorite music, podcast, or audiobook. 

What to Expect When You Go for a CT Scan

MRI vs CT scan machine

Also called a CAT scan, a CT scan can target specific areas of the body or do a full-body scan. A CT scanner is similar to an MRI machine in shape but it’s shorter and therefore more open. During the scan, you will need to lie still on a table that slides through the machine.

CT scans use multiple X-rays that pass through your body at different angles. The machine then constructs a 3D image based on variations in exposure caused by different body parts. The X-ray apparatus inside the CT scanner can detect hundreds of degrees of tissue density changes, enabling detailed images of internal organs.

What Is Ionizing Radiation and Is It Harmful? 

Ionizing radiation is a type of radiation that has enough energy to remove tightly bound electrons from atoms, creating ions. This process of ionization gives ionizing radiation its name.

Ionizing radiation can damage the cells and DNA in the body. This damage can disrupt the normal functioning of cells, potentially leading to health issues. Most of the time, the cell repairs the damage, but if the DNA is damaged severely or incorrectly repaired, this can lead to mutations, which may eventually cause cancer.

One of the most significant risks associated with ionizing radiation is the potential to develop cancer. The risk is dose-dependent. In other words, higher doses and repeated exposures increase the risk. This is why medical professionals carefully consider the necessity of procedures like X-rays or CT scans, which use ionizing radiation.

For people aged 50 to 80 who have smoked for at least 20 years, the American Cancer Society recommends a yearly screening for lung cancer with a low-dose CT scan (LDCT). A pack-year consists of smoking one pack (or about 20 cigarettes) per day for a year. When someone smokes two packs daily for 10 years, they accumulate a 20-pack-year history.

For health screening, people at high risk for developing lung cancer should only have a low-dose CT scan to minimize exposure to ionizing radiation. A patient will receive approximately five times less radiation than a standard chest CT scan.

While ionizing radiation can be harmful, its use in medicine is carefully regulated to minimize risks. The benefits of these procedures often outweigh the risks, especially when used to diagnose serious conditions. However, using ionizing radiation judiciously is always important to protect against unnecessary exposure.

MRI vs CT Scan: Which Is Better for Elective Full-Body Screening?

MRI vs CT scan: old woman smiling at the camera

For diagnostic purposes, you can rely on your doctor to recommend the imaging modality needed to confirm or “rule out” diseases. If you’re considering an elective full-body scan and want to know which is better, an MRI vs CT scan, it helps to understand the potential risks and benefits. While both imaging techniques are advanced, a full-body MRI scan is the best choice for several reasons. 

Superior Soft Tissue Contrast

Full-body MRIs excel in providing detailed images of soft tissues, including organs and the vascular system. This makes them particularly adept at identifying abnormalities such as tumors and inflammation that might not be as visible in a CT scan.

Better for Early Detection

MRI scans can detect certain conditions at an earlier stage compared to CT scans. For instance, they are more sensitive in identifying early signs of demyelinating diseases and certain cancers, allowing for earlier intervention and improving chances for successful treatment.

No Ionizing Radiation

MRI does not utilize ionizing radiation, thus making it safer for multiple scans and annual screenings compared to CT scans, where you are limited to the amount of ionized radiation.

Are MRI Scans Safe?

The short answer is yes, an MRI scan is safe and non-invasive. While an MRI scan can take longer than a CT scan, sometimes up to an hour or more, it does not expose you to any potentially harmful ionizing radiation. 

It’s also worth noting that because MRI machines use powerful magnets, they cannot be used in patients with certain types of metal implants, such as some pacemakers, cochlear implants, or metal fragments in the body. As such, you should always let the technologist know beforehand if you have any implants.

Why Is a Full-Body MRI Screening Important? 

When it comes to diagnostic testing, your doctor will always suggest the appropriate test for your suspected condition. You may also have periodic screenings as a proactive measure to monitor your health. After all, the chances of surviving cancer increases when it's diagnosed in stage I, where the cancer has not spread throughout the body.

Guidelines recommend screening for early detection of breast cancer, colon cancer, lung cancer, and cervical cancer. While most other types of cancer do not currently have recommendations for screening, that doesn't mean you can't take other measures to stay healthy.

Take Charge of Your Health and Schedule an MRI Full-Body Screening 

When it comes to a CT scan vs MRI scan, both are helpful options for specific diagnostic imaging. However, MRI screenings offer a safer imaging option for elective health screenings as they provide superior soft tissue contrast and involve no harmful radiation exposure.

The Ezra Full Body MRI scan screens for cancer and other abnormalities in up to 13 different organs, including the brain, spine, liver, gallbladder, and pancreas, among others.

Usually, doctors will only order a diagnostic test like a specialized MRI scan if you exhibit symptoms of a specific illness. At Ezra, you can get a referral for an MRI screening scan, which is ideal for when you’re asymptomatic (meaning you have no symptoms). 

As a proactive measure, you can repeat your full-body screening annually for greater peace of mind and control over your health and well-being. Remember that a full-body MRI does not replace diagnostic imaging, but it can be a helpful tool in taking charge of your health.